1. Field of the Invention
The present invention relates to an apparatus for fabricating a perforated web by a light, and in particular, the present invention relates to an apparatus and a method for continuously forming apertures or slits in a moving web by the energy of a light.
2. Description of the Related Art
There are known apparatuses and methods for forming apertures or slits in a continuously moving web using razor edges, needles, or rotatable blades (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 60-37786 filed by the inventors of this application). The method of forming apertures or slits in a wide web using a sharp cutting edge has a shortcoming in that the life of the cutting edge is short due to wear thereof and it is difficult to accurately arrange a plurality of cutting edges in position. Apparatuses and methods for forming apertures or slits in a continuously moving web using hot cutting edges to melt the web (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 61-11757) are also known. The method of forming apertures or slits using heat has a problem in that margins of apertures or slits melt to a greater extent and the shape of the margins is not clear, in addition to the above described problem concerning the cutting edges. Denaturalization of the margins of apertures or slits is not preferable when the resultant perforated web is to be subsequently stretched.
Laser techniques are being developed and used in a variety of fields, and heat energy is being used for cutting with the development of carbon dioxide lasers or YAG (yttrium, aluminum and garnet) lasers. The conventional cutting method using the laser beam is to continuously cut a web longitudinally, or to perforate holes regularly along the length of the web (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 1-46236). Also, laser beams are used for engraving or forming holes in wood or plastic plates, using a masking plate of a predetermined size (cf, for example, Japanese Unexamined Patent Publication (Kokai) No. 58-15232). Also, as an example of a laser beam applied to a moving web, the use of heat energy of a laser beam for drying the web (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 3-54053) is known.
Heat energy of the laser beam is also used to dry paintings or to weld plates by concentrating the laser beam at a point. However, the laser beam is not used for perforating a moving web since it is difficult to concentrate the laser beam at a point on the moving web, and the power of the laser beam is insufficient. Also, ultraviolet light such as used in an eximer laser is used for precision procedures in semiconductor devices, but perforating a moving web using ultraviolet light is not known.
The present invention is directed to an apparatus and a method for continuously perforating a moving web using a light such as a laser beam, infrared light, or ultraviolet light.
In the prior art, it is not possible to continuously form a plurality of discontinuous holes in a moving web having a width in a non-contact manner and at an economical speed, and though there has been a demand for continuously forming a plurality of holes along the width of a web using a masking plate, it has not been possible to continuously form a plurality of holes in the moving web because the masking plate of a predetermined size in the prior art cannot follow the moving web.
Recently, in the field of non-woven fabrics, a large amount of cross-laminated non-woven fabric comprising a warp web and a weft web have been manufactured. The warp web is fabricated by forming slits in a web so that the slits extend longitudinally about the web and by stretching the web in the direction of the slits; the weft web is fabricated by forming slits in a web so that the slits extend transversely about the web and by stretching the web in the direction of the slits; and the warp and weft webs are laminated one above the other so that the stretching directions are held crosswise to each other. Also, a reinforced film, in which a film is stretched uniaxially or biaxially and the stretched film is perforated, is used in a variety of fields.